As shown in FIG. 1, normally for high efficiency DC/DC application, a Schottky rectifier is externally added in parallel with a MOSFET device to prevent a parasitic P/N body diode in the MOSFET from turning on in order to achieve higher speed and efficiency. The requirement for the clamping effect is that forward voltage of the Schottky rectifier Vf is less than the parasitic body PN diode (˜0.7V). Besides the Schottky rectifier, a Gate-Source clamp diode with a breakdown voltage lower than gate oxide rupture voltage of the MOSFET is provided for gate oxide ESD (electrostatic discharge) protection. Moreover, a Gate-Drain clamp diode with a breakdown voltage lower than that of the MOSFET is provided for Drain-Source avalanche protection. However, assembly of those separate structures into single package with extra interconnection wires results in higher manufacturing cost, and poor performance due to increase in inductance from the extra interconnection wires.
Accordingly, it would be desirable to provide more integrated trench MOSFET device with embedded Schottky rectifier, Gate-Drain and Gate-Source clamp diodes on single chip for device shrinkage and performance improvement.